1. Field of the Invention
This invention relates to the field of laser dermatology and more particularly concerns a method and apparatus for removing hair from living skin while minimizing irritation or injury to the skin.
2. The Related Art
Location, location, location. Just as in real estate, the beauty of hair is where it rises. A forest of hair on the scalp is considered a blessing. On the upper lip it may be less desirable, most especially less desirable for females. Location on the legs is deemed also not at all attractive.
Removal of unwanted hair is commonly achieved by shaving for short-term results. Mechanical epilation with wax or other devices provides a longer respite. Several disadvantages accompany these methods. Frequently they cause irritation, folliculitis and on rare occasions scarring. There are presently several FDA-approved treatments for hair removal. Electrolysis involves resistive heating around an electrode placed deeply into a hair follicle, causing complete or partial destruction of such follicle. Such treatment is painful, tedious and only moderately effective. About 50 to 85% of treated hairs, furthermore, re-grow. There are also significant risk effects here of folliculitis and infection.
Another FDA-cleared treatment (Thermolase technique) involves exposure to a Q-switched Nd:YAG laser designed for tattoo removal, following wax epilation and topical application of a suspension of amorphous carbon particles. This treatment is mildly painful. Despite aggressive marketing, its effectiveness appears to be minimal or nonexistent. The potential complications of this treatment are those of laser surgery in general (infection, scarring, pigmentary changes), plus the risk of inadvertent tattooing by introducing carbon into the dermis through ruptured follicles. However, these complications presumably occur at an acceptably low incidence.
A safer and more effective system has been described by Dr. Rox Anderson of the Harvard Medical School and commercialized by Palomar Corporation. The system uses a ruby laser with light delivered through a transparent actively-cooled sapphire hand piece held directly in contact with the skin. The hand piece conducts heat away from the epidermis before, during and after each pulse.
Transient inflammatory reaction (erythema, edema) and pigmentary changes (hypopigmentation, hyperpigmentation) are routine and expected whenever a laser is used to injure some component of the skin. Compared with pulsed dye, Q-switched and other lasers used for cosmetic procedures, the Palomar laser produces similar skin injury followed by rapid healing requiring minimal wound care. Compared with electrolysis, in which bacteria are frequently repeatedly introduced into follicles from the skin surface by a needle-like electrode, the laser system may cause less folliculitis. Nonetheless, it is very evident there is a need for much safer procedures to avoid skin damage and to also minimize the number of treatments required for effective hair removal.
Patent References
In addition to the above general prior art, applicant is familiar with the following prior art patents of interest.
U.S. Pat. No. 5,671,735 issued to MacFarlane et al. on Sep. 30, 1997 discloses broadly the use of a colorimeter in the diagnosis of medical conditions. MacFarlane's technique involves basically the taking of a preliminary colorimeter reading of the skin before a disease condition occurs, storing this for reference in an associated computer and then later taking another reading to see if a skin color change has occurred, which, if present, may indicate a disease condition has occurred. Later readings may be used to monitor recovery. Various color instruments are disclosed. A later MacFarlane et al. U.S. Pat. No. 6,308,088 issued Oct. 23, 2001 includes expanded tables of colors including extensive hair color tables.
U.S. Pat. No. 6,015,404 issued to Altshuler et al. on Jan. 18, 2000 includes the use radiation type temperature detection devices to monitor the use of a dermatology laser device.
U.S. Pat. No. 6,050,990 issued to Tankovich et al. on Apr. 18, 2000 includes a comprehensive discussion of the use of lasers for various skin treatment purposes, including, in particular, the removal of hair, or depilation. Tankovich et al. teaches that the laser beam can be adjusted in terms of wave length, fluence, pulse repetition rate and pulse duration and that it should be adjusted in accordance with the type and condition of the patient's skin and hair. Information concerning these is to be obtained by the use of a set of questions including the color of the skin and hair and the possible use of photography to document the answers. Tankovich does not teach or even mention the use of a calorimeter to aid in determining the settings or treatment with the laser.
U.S. Pat. No. 6,149,644 issued to Xie on Nov. 21, 2000 discloses a method of treating the skin by actinic light, i.e. light sufficient to form a chemical change or induce photochemical activity, one use being hair removal. Xie discloses broadly that skin is less effected by light in the 600 to 999 nm range than hair follicles. In order to decrease the light to any specific portion of skin Xie continuously moves his light beam, whether continuous or pulsed as in a laser, along narrow contiguous paths thereby reducing the amount of energy applied to any specific spot while fully covering over a discrete period a full area.
U.S. Pat. No. 6,168,589 to Tobinick which contains a good description of the state of the art of laser depilation of the skin at the time of Applicants'filing date and suggests that the treatment should be customized according to the skin color, hair color, hair diameter and anatomy of the particular site being treated and points out that dark skinned persons and light skin persons must be treated differently as darker skin are more easily burned. Tobinick's particular solution was to divide patients into groups or categories of darkness of skin and coarseness and darkness of hair, determine the “thermal relaxation time,” i.e. the time for a uniform amount of heat to diffuse from a volume of material and adjust his laser pulses in pulse sequence time so as not to exceed the thermal relaxation time of the structure or the structures to be destroyed or damaged, i.e. the hair follicle, but to exceed the thermal relaxation time of the structures that are desired not to be damaged. There is no disclosure whatsoever of the use of a colorimeter.
U.S. Pat. No. 6,251,100 to Flock et al. teaches the use of lasers to perforate the epidermis pursuant to the application of topical anesthetics and the like to and through the skin in place of an injection. The aim is to perforate the skin with as little damage as possible. Flock sets forth a number of examples and in example 12 used a colorimeter to detect erythema or reddening of the skin as a sign of skin damage or irritation. Flock discloses the use of laser beams for other treatments as well, including, in example 17, the removal of nose hairs, but there is no disclosure of the use of a calorimeter to monitor the results.
Non-Patent References
    1. Fitzpatrick T. The validity and practicality of sun-reactive skin types I–VI. Arch Dermatol 1988; 124:869–871.    2. Nanni C A, Alster T S. Laser-assisted hair removal: side effects of Q-switched Nd:YAG, long-pulse diode and alexandrite lasers. J Am Acad Dermatol 1999; 41:167–171.    3. Takimaki, H. Measurement of skin color: practical application and theoretical consideration. The J of Med Invest 1998; 44:121–125.    4. Fullerton A, Fischer T. Laht; et al. Guidelines for measurement of skin color and erythema. Contact Dermatitis 1995; 35:1–10.